Hydra

Description

Summons a multi-headed beast of flame to reduce your enemies to ashes.

It is possible to have 6 Hydras summoned at a time, and each three-headed Hydra lasts for 10 seconds.
Individual Hydras aren't that effective, but when several of them are firing at once, the damage supplies up quickly.
Some skill is needed for placing Hydras.
It is best if several of them can concentrate their fire on the same monster, so casting a bunch of them in a row to one side is usually the best tactic, instead of simply popping them up all throughout a mass of enemies, where their shots will be dispersed into numerous targets.
It is best to pick an alternate skill to use after summonig all the Hydras and until they despawn.
Firewall or Meteor work or if you want to diversify your damage Frozen Orb, Blizzard, or Nova work well.

Hydras, despite considered minion-type in game code, do benefit from +x% Fire Damage and -x% Fire Resistance (such as provided by Rainbow Facet).
Patch 2.4: Hydra You can now spawn multiple hydras on controller when holding the button down Casting delay removed Limited max number of Hydra groups to 6.
If you are playing in Resurrected mode, the Hydra's point of emergence, as well as the fire Bolts it spits, provide a small radius of light, illuminating the dark slightly and alerting you of any enemies that may be lurking.
Even though they only last 10 seconds, Hydras are minions and cannot proc Slain Monsters Rest In Peace.
The unique paladin shield Dragonscale grants a level 10 Hydra Oskill.

Values use the listed effective skill level; synergies are not included.

Level	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	18	19	20	21	22	23	24	25	26	27	28	29	30	31	32	33	34	35	36	37	38	39	40
Duration	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s	10 s
Max Hydras	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6	6
Mana Cost	20	20.5	21	21.5	22	22.5	23	23.5	24	24.5	25	25.5	26	26.5	27	27.5	28	28.5	29	29.5	30	30.5	31	31.5	32	32.5	33	33.5	34	34.5	35	35.5	36	36.5	37	37.5	38	38.5	39	39.5
Hydra Fire Damage	14-19	19-26	25-32	30-39	36-45	41-52	47-58	52-65	60-73	67-82	75-90	82-99	90-107	97-116	105-124	112-133	122-143	131-154	141-164	150-175	160-185	169-196	181-208	192-221	204-233	215-246	227-258	238-271	252-285	265-300	279-314	292-329	306-343	319-358	333-372	346-387	360-401	373-416	387-430	400-445